As noted earlier, there has been a downward trend in the number of climbers attempting Mt Rainier's summit. From October 1st, 2005 to June 1st 2006, there were 871 registered climbers (and that included RMI stats.) During the same period the preceding year, there were 945, and that DID NOT include RMI stats.
There has also been an increase in reservations. Be advised that most of the Friday and Saturday night reservations have been taken for this season. If you want to climb a primary route, try climbing between Sunday and Wednesday.